Analysis of rejection mechanism in the rat to mouse cardiac xenotransplantation

Recent reports have demonstrated that humoral factors, especially antibodies elicited by xenoantigens, play an important role in the rejection of concordant cardiac xenografts. These induced antibodies, however, have not been well characterized. Therefore, we investigated the rejection mechanism, especially the role of humoral immunological responses in the concordant rat to mouse cardiac xenograft model. Lewis rat hearts transplanted into C3H/HeN mice were rejected in 5-6 days. The essential role of humoral factors in the rejection was demonstrated by histological analysis of the rejected hearts showing interstitial hemorrhage, scant cellular infiltration, and the dense deposition of mouse IgG, IgM, and C3 on the graft endothelial cells